<grin>
My mum gave me the courage to homeschool....why? Because she did EXACTLY what you're talking about doing. 95% of what I learned until I was 17 were things my mum taught or introduced me to.
These days, what my mum did has a name; "afterschooling". It's the combo of wanting your kids in awayschool, and yet also wanting to homeschool.
You're lucky. There are TONS of resources available. I'll toss out a few, but heads up, most you'll find in homeschooling boards or marketed toward homeschoolers. IN FACT... go to any major .edu or .org or .gov and a few of the better known .coms and you will find LESSON PLANS. From the smithsonean http://www.si.edu/ or museum of natural history, to the CIA/FBI, to national geographic. ((BTW... one we like to do around thanksgiving is the Genographic program through nat.geo.soc. & tracing family history through ancestry.com. That's known as a 'unit study' in the homeschooling world... pick ANY topic, and you cover most subjects in it, if you want to. History, geography, science, math, english))
US HISTORY (note, some of these are classic history, some are revisionist. I think for a complete history picture, one really needs to look at BOTH! Neither has the complete story, and both sides are biased.)
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Joy Hakim http://www.joyhakim.com/ & specifically (since her science stuff is new, the history stuff can get buried, but it's what she made her name in) http://www.amazon.com/History-US-11--Set/dp/0195327276/re...
Howard Zinn, Adult & young person's
http://www.amazon.com/Young-Peoples-History-United-States...
http://www.amazon.com/Peoples-History-United-States-1492-...
World History (sorry, I'm not in love with any 'complete' set... so I make up my own... hence... too many resources for me to post here). In GENERAL however, UK world history tends to be the most complete/interesting. The BBC puts a lot out there to accompany what's taught in schools, the British Museum, also. For US sources, I'm quite keen on National Geographic Society, History Channel (I know, right?)
http://www.bbc.co.uk/schools/primaryhistory
http://www.bbc.co.uk/history/forkids/
http://www.bbc.co.uk/history/
just as an example of SOME of what the brits have
Science
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http://www.noeoscience.com/ ((i know it's a religious company -I avoided even looking at it for 2 years, because I'm dumb that way-, but they just gather it all together. We're talking some of the BEST resources available for science. As a science chick (two of my majors are hard sciences), there is absolutely no religion allowed in my science. Although I'm far from agnostic, much less an atheist, the two do not belong together. Two different questions. Religion answers WHY, Science answers HOW. They don't intermingle. PHENOM science program.))
Latin
http://www.minimus-etc.co.uk/
Algebra
http://www.borenson.com/Home/EducatorsHomePage/tabid/933/...
Drats... my laptop is about to shut off and I have no cord! Anyhow, TONS of resources out there. And don't forget TED talks! Esp for older kids http://www.ted.com/talks